Conductive coating on structural ceramics for strain detection utilizing electrical measurements

Strain detection in Al₂O₃ ceramics and glass plates was investigated by coating them with an electrically conducting composite (epoxy resin and needle-like SnO₂(Sb)-coated TiO₂ filler) and by measuring surface resistance during and after loading. By adding more than 6 vol%-filler, the composite became electrically conductive. Surface electrical resistance increased with increasing strain during loading, and the degree of electrical resistance change versus strain was larger when the filler volume fraction was close to the percolation critical volume fraction. In addition, when the specimens were cyclically loaded, residual electrical resistance was observed even after removing load. The value of the residual electrical resistance was dependent on the maximum strain under the stress applied. These results suggest that estimation of maximum strain is possible by measuring resistance of the composite formed on structural ceramics. Based on the results of microfracture observation, the effect of applied stress on the electrical resistance change of electroconductive composites is discussed